1 /*
2  * Toggles a GPIO pin to power down a device
3  *
4  * Jamie Lentin <jm@lentin.co.uk>
5  * Andrew Lunn <andrew@lunn.ch>
6  *
7  * Copyright (C) 2012 Jamie Lentin
8  *
9  * This program is free software; you can redistribute it and/or modify
10  * it under the terms of the GNU General Public License version 2 as
11  * published by the Free Software Foundation.
12  *
13  */
14 #include <linux/kernel.h>
15 #include <linux/init.h>
16 #include <linux/delay.h>
17 #include <linux/platform_device.h>
18 #include <linux/gpio/consumer.h>
19 #include <linux/of_platform.h>
20 #include <linux/module.h>
21 
22 #define DEFAULT_TIMEOUT_MS 3000
23 /*
24  * Hold configuration here, cannot be more than one instance of the driver
25  * since pm_power_off itself is global.
26  */
27 static struct gpio_desc *reset_gpio;
28 static u32 timeout = DEFAULT_TIMEOUT_MS;
29 static u32 active_delay = 100;
30 static u32 inactive_delay = 100;
31 
32 static void gpio_poweroff_do_poweroff(void)
33 {
34 	BUG_ON(!reset_gpio);
35 
36 	/* drive it active, also inactive->active edge */
37 	gpiod_direction_output(reset_gpio, 1);
38 	mdelay(active_delay);
39 
40 	/* drive inactive, also active->inactive edge */
41 	gpiod_set_value_cansleep(reset_gpio, 0);
42 	mdelay(inactive_delay);
43 
44 	/* drive it active, also inactive->active edge */
45 	gpiod_set_value_cansleep(reset_gpio, 1);
46 
47 	/* give it some time */
48 	mdelay(timeout);
49 
50 	WARN_ON(1);
51 }
52 
53 static int gpio_poweroff_probe(struct platform_device *pdev)
54 {
55 	bool input = false;
56 	enum gpiod_flags flags;
57 
58 	/* If a pm_power_off function has already been added, leave it alone */
59 	if (pm_power_off != NULL) {
60 		dev_err(&pdev->dev,
61 			"%s: pm_power_off function already registered",
62 		       __func__);
63 		return -EBUSY;
64 	}
65 
66 	input = device_property_read_bool(&pdev->dev, "input");
67 	if (input)
68 		flags = GPIOD_IN;
69 	else
70 		flags = GPIOD_OUT_LOW;
71 
72 	device_property_read_u32(&pdev->dev, "active-delay-ms", &active_delay);
73 	device_property_read_u32(&pdev->dev, "inactive-delay-ms",
74 				 &inactive_delay);
75 	device_property_read_u32(&pdev->dev, "timeout-ms", &timeout);
76 
77 	reset_gpio = devm_gpiod_get(&pdev->dev, NULL, flags);
78 	if (IS_ERR(reset_gpio))
79 		return PTR_ERR(reset_gpio);
80 
81 	pm_power_off = &gpio_poweroff_do_poweroff;
82 	return 0;
83 }
84 
85 static int gpio_poweroff_remove(struct platform_device *pdev)
86 {
87 	if (pm_power_off == &gpio_poweroff_do_poweroff)
88 		pm_power_off = NULL;
89 
90 	return 0;
91 }
92 
93 static const struct of_device_id of_gpio_poweroff_match[] = {
94 	{ .compatible = "gpio-poweroff", },
95 	{},
96 };
97 
98 static struct platform_driver gpio_poweroff_driver = {
99 	.probe = gpio_poweroff_probe,
100 	.remove = gpio_poweroff_remove,
101 	.driver = {
102 		.name = "poweroff-gpio",
103 		.of_match_table = of_gpio_poweroff_match,
104 	},
105 };
106 
107 module_platform_driver(gpio_poweroff_driver);
108 
109 MODULE_AUTHOR("Jamie Lentin <jm@lentin.co.uk>");
110 MODULE_DESCRIPTION("GPIO poweroff driver");
111 MODULE_LICENSE("GPL v2");
112 MODULE_ALIAS("platform:poweroff-gpio");
113